You dont need to have grown up in the city at all. Your background is what you did before you became an adventurer. So if you were an outlander for example you grew up outside of the city. You could have moved to baldurs gate relativly shortly before beeing snagged by the nautiloid. Or you could have been there for years.
Given how everyone is back to lvl 1 its hard to tell how powerfull our characters were prior to the kidnapping. And how long they were in the city.
Characters like druids generally avoid big cities as well. So maybe they were visiting for some special mission?
